Analog baseband filter apparatus for multi-band and multi-mode wireless transceiver and method for controlling the filter apparatus

ABSTRACT

An analog baseband filter apparatus for a multi-mode and multi-band wireless transceiver and a method for controlling the analog baseband filter apparatus are provided. The analog baseband filter apparatus includes a plurality of Radio Frequency (RF) units, each of the plurality of RF units being for receiving RF signals of one of a plurality of frequency bands and outputting baseband signals, a plurality of filter blocks for filtering and amplifying the baseband signals, and a switching unit for connecting at least two of the plurality of RF units to at least one of the plurality of filter blocks according to a selected communication mode, wherein the at least one of the plurality of filter blocks is configured to be connected to a capacitor region of an adjacent filter block from among the plurality of filter blocks.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 13/864,768, filed on Apr. 17, 2013, which claimed the benefitunder 35 U.S.C. §119(e) of a U.S. Provisional patent application filedon Aug. 31, 2012 in the U.S. Patent and Trademark Office and assignedSer. No. 61/695,712, and under 35 U.S.C. §119(a) of a Korean patentapplication filed on Jan. 2, 2013 in the Korean Intellectual PropertyOffice and assigned Serial No. 10-2013-0000361, the entire disclosure ofeach of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a wireless communication system. Moreparticularly, the present invention relates to an apparatus forfiltering an analog baseband signal in a multi-mode and multi-bandwireless transceiver and a method for controlling the apparatus.

BACKGROUND

In a receiver of wireless communication, an analog filter is used tofilter unnecessary noise from a signal that is demodulated into abaseband by a mixer and to select a signal of a desired channel. In theanalog filter, an accurate cut-off frequency setting has a significantinfluence upon system performance.

Generally, a filter has an input-to-output gain value which changes as afrequency value increases, and the filter has also a pass band and astop band. A cut-off frequency f_(c) refers to a boundary frequency thatis between the pass band and the stop band. A Low Pass Filter (LPF)defines a cut-off frequency f_(c), which is a frequency having a gainvalue which is 3 dB lower than a gain value of a direct current or a lowfrequency in the pass band. The cut-off frequency f_(c) is determined bya feedback resistor and a feedback capacitor, both of which are used inthe analog filter.

A baseband used in mobile communication systems covers a very largerange of frequencies from a bandwidth of 100 kHz for 2nd Generation (2G)communication systems to a bandwidth of 20 MHz for 3rd Generation (3G)or 4th Generation (4G) communication systems, wherein the highestbandwidth of the baseband is about 100 times the lowest bandwidth. Amulti-mode mobile terminal, which uses a 2G mode for voice communicationand uses a 3G or 4G (hereinafter, ‘3G/4G’) mode for data communication,should have a multi-mode and multi-band wireless transceiver that usesan analog baseband filter that is capable of supporting the foregoingdiverse bandwidths of the baseband.

However, a resistor value, which may also be referred to as aresistance, and a capacitor value, which may also be referred to as acapacitance, which determine the cut-off frequency f_(c) of the analogbaseband filter change according to temperature and process conditions,and the resistance and capacitance are difficult to accurately estimate,such that in an actual environment, the cut-off frequency f_(c) may bedifferent from a target value. Hence, the cut-off frequency f_(c) iscorrected by controlling a variable resistor and/or a variable capacitorwith a digital algorithm, and an error of correction needs to be lessthan 4%.

The cut-off frequency f_(c) is inversely proportional to a product of aresistor value and a capacitor value, such that in order to process asignal in a low band, such as 2G, a resistor and a capacitor having verylarge values are needed, and accordingly, an area and/or physical sizeof the analog filter may increase. A capacitor for processing a low bandof 2G may be several times larger in size than that in a 3G/4G, thusincreasing a circuit area of the analog filter several times. As such,when the 3G/4G mode operates, the circuit area of the analog filtersignificantly increases due to the idle 2G mode, thus increasing theprocessing cost with respect to power, computation and other similarresources. Moreover, as the circuit area increases, a path length of asignal travelling through the circuit increases, thus increasing anerror of the signal and noise, and thus degrading characteristics of thesignal.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide an apparatus for filtering an analog signal in awireless transceiver and a method for controlling the apparatus.

Another aspect of the present invention is to provide a variable-gainamplifier and a variable-frequency filter for processing diverse signalbands using a single architecture.

Another aspect of the present invention is to provide an apparatus forminimizing a circuit area of an analog baseband filter for multi-modeand multi-band use and a method for controlling the apparatus.

Another aspect of the present invention is to provide an apparatus forsharing a capacitor of a diversity path in a multi-mode and multi-bandwireless transceiver and for improving an architecture of input andfeedback resistors, and a method for controlling the apparatus.

Another aspect of the present invention is to provide an apparatus inwhich a plurality of analog baseband filters are concatenated and usedin a multi-mode and multi-band receiver and a method for controlling theapparatus.

In accordance with an aspect of the present invention, an analogbaseband filter apparatus for a multi-mode and multi-band wirelesstransceiver is provided. The analog baseband filter apparatus includes aplurality of Radio Frequency (RF) units, each of the plurality of RFunits being for receiving RF signals of one of a plurality of frequencybands and outputting baseband signals, a plurality of filter blocks forfiltering and amplifying the baseband signals, and a switching unit forconnecting at least two of the plurality of RF units to at least one ofthe plurality of filter blocks according to a selected communicationmode, wherein the at least one of the plurality of filter blocks isconfigured to be connected to a capacitor region of an adjacent filterblock from among the plurality of filter blocks.

In accordance with another aspect of the present invention, a method forcontrolling an analog baseband filter apparatus for a multi-mode andmulti-band wireless transceiver is provided. The method includesconnecting a plurality of Radio Frequency (RF) units, each of theplurality of RF units being for receiving RF signals of a High Band (HB)and outputting baseband signals to a plurality of filter blocks forrespectively filtering and amplifying the baseband signals in a firstcommunication mode which uses the HB and connecting two RF units fromamong the plurality of RF units to second and third filter blocks of theplurality of filter blocks in a second communication mode which uses aLow Band (LB), wherein, when in the second communication mode, capacitorregions of the second and third filter blocks are respectively connectedwith capacitor regions of respectively adjacent first and fourth filterblocks.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating a structure of an analog filter havinga characteristic function of a primary frequency filter according to anexemplary embodiment of the present invention;

FIGS. 2A and 2B are a block diagram and a floor plane illustrating ananalog baseband filter, respectively according to an exemplaryembodiment of the present invention;

FIG. 3A is a diagram illustrating a structure of a reception apparatuswhich supports a plurality of high-band modes according to an exemplaryembodiment of the present invention;

FIG. 3B is a diagram illustrating a structure of a terminal apparatuswhich supports first and second high-band modes according to anexemplary embodiment of the present invention;

FIGS. 4A and 4B are a block diagram and a floor plan illustrating ananalog baseband filter apparatus according to an exemplary embodiment ofthe present invention, respectively;

FIGS. 5A through 5C are diagrams for describing a mode change of ananalog filter according to an exemplary embodiment of the presentinvention;

FIG. 6 is a diagram illustrating a resistor block which varies accordingto a mode according to an exemplary embodiment of the present invention;

FIGS. 7A through 7F are diagrams illustrating diverse connections of aresistor block according to an exemplary embodiment of the presentinvention;

FIG. 8 is a circuit diagram of an analog baseband filter apparatusaccording to an exemplary embodiment of the present invention; and

FIGS. 9A and 9B are diagrams illustrating in detail connection ofcapacitors according to an exemplary embodiment of the presentinvention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures.

DETAILED DESCRIPTION

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

The present invention is not limited by exemplary embodiments providedin the drawings and the specification. Throughout the drawings, likereference numerals refer to like members. The drawings have beensimplified and relatively exaggerated to emphasize the features of thepresent invention, and dimensions in the drawings do not accuratelymatch the dimensions of actual products of the present invention. Thoseof ordinary skill in the art may easily modify dimensions, such aslength, circumference, and thickness, of each component from thedisclosure of the drawings for application into an actual product, andit will be obvious to those of ordinary skill in the art that suchmodification falls within the scope of the present invention.

The following exemplary embodiments of the present invention relate toan analog filter for filtering an analog signal, and more particularly,to a multi-mode and multi-band analog baseband filter. An AnalogBaseBand (ABB) filter may be used for wireless transceivers whichsupport bandwidths of different wireless communication techniques, suchas Global System for Mobile communications (GSM), Enhanced Data GSMEnvironment (EDGE), High Speed Packet Access (HSPA), Wideband CodeDivision Multiple Access (WCDMA), Long Term Evolution (LTE) 1.4M, LTE3M, LTE 5M, LTE 10M, LTE 15M, and LTE 20M, and any other similar and/orsuitable wireless communication technique.

FIG. 1 is a diagram illustrating a structure of an analog filter havinga characteristic function of a primary frequency filter according to anexemplary embodiment of the present invention.

Referring to FIG. 1, an analog filter 100 includes an operationamplifier (OP AMP) 150 which receives an input voltage Vin at a negative(−) terminal through an input resistor 160 having a resistance value ofR_(a) and a positive (+) terminal that is grounded. The analog filter100 also includes a feedback resistor 170, having a resistance value ofR_(b), and a feedback capacitor 180, having a capacitance value of C,which are both connected between the negative (−) terminal and an outputVout of the OP AMP 150. The resistors 160 and 170 may be variableresistors, and a gain value and a cut-off frequency of the analog filter100 may be changed by changing resistor values of the resistors 160 and170. A gain value and a cut-off frequency of a direct current of theanalog filter 100 are expressed as follows:

Gain: R _(b) /R _(a) ,fc:1/(2πR _(b) C)  Equation 1.

In Equation 1, R_(a) indicates a resistor value of the input resistor160, R_(b) indicates a resistor value of the feedback resistor 170, andC indicates a capacitance of the feedback capacitor 180. As such, thecut-off frequency f_(c) is inversely proportional to the feedbackresistor value R_(b) and the feedback capacitor value C. Herein, R_(b)and C are controlled by a digital code in order to increase linearly orexponentially.

A receiver filter applied to a Radio Frequency (RF) circuit maytypically be composed of three through seven stages by seriallycombining a Real Pole (RP) filter having one RP, as illustrated in FIG.1, and a plurality of Bi-Quad (BQ) filters, for example BQ filters twothrough six, having one or more RPs.

A baseband used in mobile communication systems may cover a very largerange from a bandwidth of 100 kHz, for 2G communication systems such asGSM, to a bandwidth of 20 MHz, for 4G communication systems such as LTE.Table 1 shows examples of cut-off frequencies for standardized mobilecommunication basebands.

TABLE 1 Mode 2G 3G 4G Standard GSM EDGE HSPA SC HSPA DC LTE1.4 LTE3 LTE5LTE10 LTE15 LTE20 BW 100 kHz 100 kHz 1.92 MHz 4.42 MHz 615 kHz 1.5 MHz2.5 MHz 5 MHz 7.5 MHz 10 MHz

Herein, mobile communication systems of HSPA Single Carrier (SC) andHSPA Dual Carrier (DC) are included. In a 3G or 4G (hereinafter,‘3G/4G’) mode, an additional frequency band for diversity may be usedthrough an additional reception antenna, in addition to a frequency bandfor a reception antenna used for basic services. With respect to theexemplary embodiments described herein, the two frequency bands will bereferred to as a Primary (PRX) High Band (HB) for the basic services anda Diversity (DRX) HB for the additional frequency band.

FIGS. 2A and 2B are a block diagram and a floor plane of an analogbaseband filter, respectively according to an exemplary embodiment ofthe present invention.

Referring to FIG. 2A, an analog baseband filter includes a firstfiltering and amplifying path 210 and a second filtering and amplifyingpath 215 for an In-phase (I) signal and a Quadrature-phase (Q) signal ofa 3G/4G mode PRX HB. The analog baseband filter also includes a thirdfiltering and amplifying path 220 and a fourth filtering and amplifyingpath 225 for I and Q signals of a 3G/4G mode DRX HB, and a fifthfiltering and amplifying path 230 and a sixth filtering and amplifyingpath 235 for I and Q signals of a 2G mode Low Band (LB).

The respective filtering and amplifying paths 210 through 235 includeI/Q chains for filtering and amplifying (hereinafter,filtering/amplifying) the I or Q signal. More specifically, the firstfiltering/amplifying path 210 includes an RP filter 202 connected to apositive (+) input IP and a negative (−) input IN of the I signal of thePRX HB, a first BQ filter 204 and a second BQ filter 206, and aVariable-Gain Amplifier (VGA) 208 connected to an IP output OIP and anIN output OIN. The RP filter 202, the first and second BQ filters 204and 206, and the VGA 208 are sequentially serially connected. The secondfiltering/amplifying path 215 includes three filters and a VGA in amanner similar to the first filtering/amplifying path 210, and receivesQP and QN and outputs OQP and OQN. Likewise, the otherfiltering/amplifying paths 220 through 234 also include three filtersand a VGA which are connected in series.

Referring to FIG. 2B, a floor plan of a circuit corresponding to theanalog baseband filtering/amplifying paths 210 through 235 of FIG. 2A isillustrated. FIG. 2B shows a connection relationship between thefiltering/amplifying paths 210 through 235 and RF units for inputtingI/Q signals to the filtering/amplifying paths 210 through 235 and aninternal arrangement of the respective filtering/amplifying paths 210through 235.

A PRX RF I unit 242 receives an RF signal of the PRX HB, frequencydown-converts the received RF signal into an I signal of a baseband, andforwards the baseband I signal to a corresponding first filter blockhaving a capacitor region 260 and an active region 262, which isequivalent to the first filtering/amplifying path 210 of FIG. 2A. A PRXRF Q unit 244 receives a Q signal of the PRX HB and forwards thereceived Q signal to a corresponding second filter block having anactive region 264 and a capacitor region 266. A DRX RF I unit 246receives an I signal of the DRX HB and forwards the received I signal toa corresponding third filter block having a capacitor region 268 and anactive region 270. A DRX RF Q unit 248 receives a Q signal of the DRX HBand forwards the received Q signal to a corresponding fourth filterblock having an active region 272 and a capacitor region 274. Likewise,filter blocks having the active regions and capacitor regions 264through 274 are equivalent to the second through fourthfiltering/amplifying paths 215 through 225 of FIG. 2A.

A 2G RF Q unit 250 receives an RF signal of a 2G LB, frequencydown-converts the received RF signal to a Q signal of the baseband, andforwards the baseband Q signal to a corresponding fifth filter blockhaving a capacitor region 276 and an active region 278, which isequivalent to the fifth filtering/amplifying path 230 of FIG. 2A. A 2GRF I unit 252 receives an RF signal of a 2G LB, frequency down-convertsthe received RF signal to an I signal of the baseband, and forwards thebaseband I signal to a corresponding sixth filter block having an activeregion 280 and a capacitor region 282, which is equivalent to the sixthfiltering/amplifying path 235 of FIG. 2A.

Elements of the filter block 210 of FIG. 2A may be classified intopassive elements such as resistors or capacitors and active elementssuch as OP AMPs. Thus, the first filter block includes the capacitorregion 260 including a capacitor bank and resistors and an active region262 including OP AMPs. Similarly, the second through sixth filter blocks(264 through 282) include capacitor regions 266, 268, 274, 276, and 282and active regions 264, 270, 272, 278, and 280, respectively. Tofacilitate circuit manufacturing, adjacent filter blocks are typicallyconfigured such that identical regions are adjacent to each other. Forexample, the active region 262 of the first filter block is disposedadjacent to the active region 264 of the second filter block, and thecapacitor region 266 of the second filter block is disposed adjacent tothe capacitor region 268 of the third filter block. The active region270 of the third filter block is disposed adjacent to the active region272 of the fourth filter block. Likewise, the capacitor region 274 ofthe fourth filter block is disposed adjacent to the capacitor region 276of the fifth filter block, and the active region 278 of the fifth filterblock is disposed adjacent to the active region 280 of the sixth filterblock. In other words, I path and Q path of each band are symmetric toeach other on the floor plan.

As stated above, since the cut-off frequency f_(c) is inverselyproportional to a product of a resistor value and a capacitor value, toprocess an LB signal such as a 2G signal, a resistor and a capacitorhaving very large values are required. As a result, the circuit area ofthe capacitor regions 276 and 282 of the fifth and sixth filter blocksfor the 2G mode is much larger, i.e., about 2 times larger, than that ofthe capacitor regions 260, 266, 268, and 274 for the 3G/4G mode.

If the entire range of the baseband is processed merely with control ofresistor values, instead of using capacitors occupying a large area,then the circuit area may be reduced, however an influence of noise mayincrease. More specifically, noise generated in a real wirelessenvironment is proportional to an input resistor value at the firstfilter stage 202, as expressed by Equation 2, and the noise ismultiplied by a gain, such that the noise appears in the output signalsOIP and OIN.

V _(N) ²=4kTR·BW  Equation 2

In Equation 2, V_(N) indicates a noise voltage, k indicates a Boltzmannconstant (=1.38*10−23), T indicates an absolute temperature, R indicatesan input resistor value of the first filter stage 202, and BW indicatesa bandwidth.

A noise figure required for an analog baseband filter is less than 30dB, which corresponds to noise introduced at a resistance of 50 kΩ thatis 100 times a reference resistance of 50Ω. Therefore, an input resistorvalue of each filter cannot be higher than a maximum of 50 kΩ. Inaddition, a gain of each filter ranges from 0 dB to 24 dB, such that afeedback resistor value is ⅙ through 1 of the input resistor value. Asdescribed above, in order to process all bandwidths of 2G and 4G, a100-times or 100-fold frequency range from the lowest frequency isrequired. Hence, in order to obtain a desired cut-off frequency withcontrol of a resistor value instead of a capacitance value, a 1600-foldgain range from the minimum gain is needed. At the same time, in orderto obtain a 24 dB gain when an input resistor value of 500Ω, which is1/100 of a maximum input resistor value of 50 kΩ a is used, then thefeedback resistor value is 31.25 Ω according to Equation 2, thussignificantly degrading output impedance, and thus failing in obtaininga desired gain and intensifying signal distortion.

Therefore, in the following exemplary embodiment of the presentinvention, an analog baseband filter circuit is configured to allowsignal chains for frequency bands of an HB mode to be used also in an LBmode. For example, Q channel signal paths for a PRB HB and a DRX HB ofan HB mode are shared with the LB mode. As another example, I channelsignal paths for the PRB HB and the DRX HB of the HB mode are sharedwith the LB mode.

FIG. 3A is a diagram illustrating a structure of a reception apparatuswhich supports a plurality of HB modes according to an exemplaryembodiment of the present invention.

Referring to FIG. 3A, the reception apparatus includes a plurality of RFunits including a first RF unit 302, and a second RF unit 304 through anNth RF unit 306 for RF processing of an HB or LB signal. However, thepresent invention is not limited thereto, and the reception apparatusmay include any suitable and or similar number of RF units. Thereception apparatus also includes a plurality of Analog BaseB and (ABB)blocks including a first ABB block 312, and a second ABB block 314through an Nth ABB block 316 for baseband signal processing. However,the present invention is not limited thereto, and the receptionapparatus may include any suitable and/or similar number of RF units.Additionally, the reception apparatus includes a switching unit 310 forconnection between the RF units 302, 304, and 306 and the ABB blocks312, 314, and 316, and a controller 300 for controlling the switchingunit 310 according to a selected communication mode.

The first through Nth RF units 302, 304, and 306 perform RF processingfor an I or Q path of a frequency band according to the selectedcommunication mode. In an exemplary embodiment of the present invention,the first RF unit 302 is configured to perform signal processing of afirst HB and signal processing of an LB. In an HB mode, the first RFunit 302 receives an RF signal of the HB and converts the received RFsignal into an I or Q signal of a baseband, and in an LB mode, the firstRF unit 302 receives an RF signal of an LB and converts the received RFsignal to an I or Q signal of a baseband.

The first through Nth ABB blocks 312, 314, and 316 individually processa baseband signal corresponding to an HB or process a baseband signalcorresponding to an LB in association with other adjacent ABB blocks. Tobe more specific, the first ABB block 312 and the second ABB block 314individually operate in an HB mode, however, in an LB mode, the twoblocks 312 and 314 are concatenated to process a signal of an LB. Inorder to process the signal of the LB together, the first ABB block 312and the second ABB block 314 are arranged symmetrically to each other.More specifically, a capacitor region of the first ABB block 312 isdisposed adjacent to a capacitor region of the second ABB block 314,such that the capacitor regions of the first ABB block 312 and thesecond ABB block 314 may be connected to each other in the LB mode.

The switching unit 310 connects the first through Nth RF units 302, 304,and 306 with the first through Nth ABB blocks 312, 314, and 316according to the selected communication mode, under control of thecontroller 300. The controller 300 controls the overall operation of thereception apparatus, and controls the switching unit 310 according towhether a desired communication mode is the LB mode or the HB mode. Morespecifically, in the HB mode, the switching unit 310 connects the firstRF unit 302 to the first ABB block 312, the second RF unit 304 to thesecond ABB block 314, and the Nth RF unit 306 to the Nth ABB block 316.

In the LB mode, if the first RF unit 302 is configured to receive the RFsignal of the LB, the switching unit 310 connects the first RF unit 302to the second ABB block 314 and a capacitor region of the second ABBblock 314 is expanded to include a capacitor region of the first ABBblock 312. For such expansion, the capacitor region of the second ABBblock 314 is disposed adjacent to the capacitor region of the first ABBblock 312, such that in the LB mode, the two capacitor regions areconcatenated to each other to process, i.e., to filter and amplify, abaseband signal corresponding to the LB. Likewise, at least two otherABB blocks are connected to other RF units in order to process abaseband signal corresponding to the LB.

FIG. 3B is a diagram illustrating a structure of a terminal apparatuswhich supports first and second HB modes according to an exemplaryembodiment of the present invention.

Referring to FIG. 3B, the terminal apparatus includes a first RF I unit322 and a first RF Q unit 324 for I/Q paths of a first HB and a secondRF I unit 326 and a second RF Q 328 for I/Q paths of a second HB, afirst ABB I block 332 and a first ABB Q block 334 for baseband I/Q pathscorresponding to the first HB, a second ABB Q block 336 and a second ABBI block 338 for baseband I/Q paths corresponding to the second HB, aswitching unit 330 for connection between the RF units 322, 324, 326,and 328 and the ABB blocks 332, 334, 336, and 338, and a controller 340for controlling the switching unit 330 according to a communicationmode.

The first RF I unit 322 and the first RF Q unit 324 for an I path of thefirst HB may be configured to operate as RF units for an I or Q path ofan LB. Furthermore, the second RF I unit 326 and the second RF Q unit328 for an I path of the second HB may be configured to operate as RFunits for I and Q paths of the LB. When the terminal operates in a 2Gmode, the first RF I unit 322 and the first RF Q unit 324 or the secondRF I unit 326 and the second RF Q unit 328 receive an RF signal of a 2Gband and convert the received RF signal into baseband I/Q signals. Ifthe terminal operates in 3G/4G modes, the first RF I/Q units 322 and 324receive RF signals of the first HB and convert the RF signals intobaseband I/Q signals, and the second RF I unit 326 and the second RF Qunit 328 receive RF signals of the second HB and convert the RF signalsinto baseband I/Q signals.

The ABB blocks 332, 334, 336, and 338 are configured to individuallyprocess I/Q signals corresponding to the first or second HB or toprocess I/Q signals corresponding to the LB in pairs. More specifically,the first ABB I block 332 and the first ABB Q block 334 individuallyoperate in the 3G/4G modes, but in the 2G mode, they process an I signalor a Q signal of the LB. Likewise, the second ABB Q block 336 and thesecond ABB I block 338 individually operate in the 3G/4G modes, but inthe 2G mode, they process a Q signal or an I signal of the LB together.To process the I/Q signals of the 2G mode together, the first ABB Iblock 332 and the first ABB Q block 334 and the second ABB I block 336and the second ABB Q block 338 are disposed symmetrically to each other.To be more specific, the second ABB Q block 336 is disposed adjacent tothe first ABB Q block 334 such that in the 2G mode, capacitor regionsincluded in the first ABB I block 332 and the first ABB Q block 334 areconnected to each other and capacitor regions included in the second ABBI block 336 and the second ABB Q block 338 are connected to each other.

The switching unit 310 connects the RF units 322, 324, 326, and 328 withthe ABB blocks 332, 334, 336, and 338 according to a selectedcommunication mode under control of the controller 340. The controller340 controls the overall operation of the terminal apparatus andcontrols the switching unit 330 according to whether a desiredcommunication mode is the 2G mode or the 3G/4G modes. More specifically,in the 3G/4G modes, the switching unit 330 connects the first RF I unit322 to the first ABB I block 332, the first RF Q unit 324 to the firstABB Q block 334, the second RF I unit 326 to the second ABB I block 338,and the second RF Q unit 328 to the second ABB Q block 336.

In the 2G mode, if the first RF I unit 322 and the first RF Q unit 324are configured to receive an RF signal of a 2G LB, then the switchingunit 330 connects the first RF Q unit 324 to the first ABB Q block 334and the capacitor region of the first ABB Q block 334 is expanded toinclude the capacitor region of the first ABB I block 332. For such anexpansion, the capacitor region of the second ABB Q block 336 isdisposed adjacent to the capacitor region of the second ABB I block 338.

In another exemplary embodiment of present invention, in the 2G mode, ifthe second RF I unit 326 and the second RF Q unit 328 are configured toreceive an RF signal of the 2G LB, the switching unit 330 connects thesecond RF I unit 326 to the first ABB Q block 334 and the capacitorregion of the first ABB Q block 334 is expanded to include the capacitorregion of the first ABB I block 332. The switching unit 330 connects thesecond RF Q unit 328 to the second ABB Q block 336 and the second ABB Qblock 336 is expanded to include the capacitor region of the second ABBI block 338.

FIGS. 4A and 4B are a block diagram and a floor plan illustrating ananalog baseband filter apparatus according to an exemplary embodiment ofthe present invention, respectively.

Referring to FIG. 4A, an analog baseband filter apparatus includes afirst filtering/amplifying path 410 for an I signal of a PRX HB mode ofthe 3G/4G modes, a second filtering/amplifying path 420 for both a Qsignal of the PRX HB mode and I/Q signals of an LB mode, a thirdfiltering/amplifying path 430 for both a Q signal of a DRX HB mode andQ/I signals of the LB mode, and a fourth filtering/amplifying path 440for an I signal of the DRX HB mode.

Each of the filtering/amplifying paths 410, 420, 430, and 440 include anRP filter, such as an RP filter 412, connected with (+) and (−) inputs,a first BQ filter, such as a first BQ filter 414, a second BQ filter,such as a second BQ filter 416, and a VGA, such as VGA 418, connected to(+) and (−) outputs.

As described before, the filtering/amplifying paths 420 and 430 of aprimary Q channel and a diversity Q channel are configured to be usedadditionally for filtering/amplification of the 2G mode. That is, thefiltering/amplifying paths 420 and 430 are shared for primary/diversityQ channels and I/Q channels of the 2G mode. In another exemplaryembodiment of the present invention, primary/diversity I channels mayshare filtering/amplifying paths with the 2G mode, which may be easilyconducted by those of ordinary skill in the art based on the drawingsand the following description of the present exemplary embodiment.

As the filtering/amplifying paths 430 and 420 of the diversity I and Qchannels are alternately disposed, the filtering/amplifying path 430 ofthe diversity Q channel is disposed adjacent to the filtering/amplifyingpath 420 of the primary Q channel such that when thefiltering/amplifying paths 420 and 430 operate in the 2G mode, I channelpath and Q channel path of the 2G mode are not spaced apart from eachother.

Referring to FIG. 4B, a floor plan of a circuit corresponding to theanalog baseband filtering/amplifying paths 410 through 440, which areshown in FIG. 4A, is illustrated. FIG. 4B shows a connectionrelationship between filter blocks corresponding to thefiltering/amplifying paths 410 through 440 and RF units and an internalarrangement of the respective filter blocks.

Referring to FIG. 4B, a PRX RF I unit 452 and a PRX RF Q unit 454 for Iand Q signals of a PRX HB and a DRX RF I unit 456 and a DRX RF Q unit458 for I and Q signals of the DRX HB are shown. All or at least two ofthe PRX RF I unit 452 and the PRX RF Q unit 454 and the DRX RF I unit456 and the DRZ RF Q unit 458 are configured to process I/Q signals ofthe 2G mode.

In the 3G/4G modes, the PRX RF I unit 452 receives an RF signal of thePRX HB, frequency down-converts the received RF signal to an I signal ofa baseband, and forwards the baseband I signal to the correspondingfirst filter block having an active region 460 and a capacitor region462. The PRX RF Q unit 254 receives a Q signal of the PRX HB andforwards the received Q signal to the corresponding second filter blockhaving a capacitor region 464 and an active region 466, and the DRX RF Iunit 456 receives an I signal of the DRX HB and forwards the received Isignal to the corresponding third filter block having an active region468 and a capacitor region 470. The DRX RF Q unit 458 receives a Qsignal of the DRX HB and forwards the received Q signal to thecorresponding fourth filter block having a capacitor region 472 and anactive region 474. In the 2G mode, the PRX RF I unit 452 and the PRX RFQ unit 454 or the DRX RF I unit 456 and the DRZ RF Q unit 458 receive anRF signal of the 2G LB, frequency down-convert the received RF signal toI/Q signals of the baseband, and forward the baseband I/Q signals to thecorresponding second and third filter blocks, in which capacitor regions464 and 470 of the second and third filter blocks are expanded toinclude capacitor regions of other adjacent filter blocks.

The filter blocks are equivalent to the filtering/amplifying paths 410through 440 of FIG. 4A. The first filter block includes the activeregion 460 including active elements such as a resistor and an OP AMPand the capacitor region 462 including capacitors, and is equivalent tothe first filtering/amplifying path 410 of FIG. 4A. The second filterblock includes the capacitor region 464 and the active region 466, andis equivalent to the second filtering/amplifying path 420 of FIG. 4A.The capacitor region 464 of the second filter block is disposed adjacentto the capacitor region 462 of the first filter block and is connectedwith the capacitor region 462 of the first filter block when operatingin the 2G mode, thus expanding the capacitance of the capacitor. Thethird filter block includes the active region 468 and the capacitorregion 470, and is equivalent to the third filtering/amplifying path 430of FIG. 4A. The fourth filter block includes the capacitor region 472and the active region 474, and is equivalent to the fourthfiltering/amplifying path 440 of FIG. 4A. The capacitor region 470 ofthe third filter block is disposed adjacent to the capacitor region 472of the fourth filter block and is connected with the capacitor region472 of the fourth filter block when operating in the 2G mode, thusexpanding the capacitor's capacitance.

As such, capacitor regions of two filter blocks are disposed adjacent toeach other, such that the two capacitor regions are connected to supportprocessing of a 2G mode signal.

FIGS. 5A through 5C are diagrams for describing a mode change of ananalog filter according to an exemplary embodiment of the presentinvention.

Referring to FIG. 5A, a signal flow in the 3G/4G modes is shown,referring to FIG. 5B, a signal flow when the PRX RF I unit 452 and thePRX RF Q unit 454 are used for the 2G mode is shown, and referring toFIG. 5C, a signal flow when the DRX RF I unit 456 and the DRX RF Q unit458 are used for the 2G mode is shown.

In FIG. 5A, the PRX RF I unit 452 receives an RF signal of the PRX HB,frequency down-converts the received RF signal to an I signal of thebaseband, and forwards the baseband I signal to the first filter block.The active region 460 and the capacitor region 462 of the first filterblock operate for the I signal of the PRX HB. The PRX RF Q unit 454receives an RF signal of the PRX HB, frequency down-converts thereceived RF signal to a Q signal of the baseband, and forwards thebaseband Q signal to the second filter block. The capacitor region 464and the active region 466 of the second filter block operate for the Qsignal of the PRX HB.

The DRX RF I unit 456 receives an RF signal of the DRX HB, frequencydown-converts the received RF signal to an I signal of the baseband, andforwards the baseband I signal to the fourth filter block. The capacitorregion 472 and the active region 474 of the fourth filter block operatefor the I signal of the DRX HB. The DRX RF Q unit 458 receives an RFsignal of the DRX HB, frequency down-converts the received RF signal toa Q signal of the baseband, and forwards the baseband Q signal to thethird filter block. The active region 468 and the capacitor region 470of the third filter block operate for the Q signal of the DRX HB.

As such, in the 3G/4G modes, a PRX path and a DRX path are independentlyoperated, and outputs from the RF units 452, 454, 456, and 458 areforwarded to the corresponding filter blocks through a switching unit500.

As shown in FIGS. 5B and 5C, in the 2G mode, filter inputs are forwardedfrom the PRX RF I unit 452 and the PRX RF Q unit 454 or from the DRX RFI unit 456 and the DRX RF Q unit 458, such that they have a generalpurpose. When the PRX RF I unit 452 and the PRX RF Q unit 454 are usedfor the 2G mode, the DRX RF I unit 456 and the DRX RF unit 458 areturned off in order to prevent unnecessary power consumption. On theother hand, when the DRX RF I unit 456 and the DRX RF Q unit 458 areused for the 2G mode, the PRX RF I unit 452 and the PRX RF Q unit 454are turned off to prevent unnecessary power consumption.

When the filter inputs are forwarded from the PRX RF I unit 452 and thePRX RF Q unit 454, channels are formed between the PRX RF I unit 452 andthe PRX RF Q unit 454 and some of the regions 462 through 472 of thecorresponding filter blocks through a switching unit 510, as shown inFIG. 5B.

More specifically, the PRX RF I unit 452 receives an RF signal of theLB, frequency down-converts the received RF signal to an I signal of thebaseband, and forwards the baseband I signal to the third filter blockthrough the switching unit 510. The capacitor region 470 of the thirdfilter block is connected with the capacitor region 472 of the fourthfilter block, such that the active region 468 and the capacitor region470 of the third filter block and the capacitor region 472 of the fourthfilter block operate for the I signal of the LB. Variable capacitorsincluded in the capacitor region 472 of the fourth filter block vary bya control signal of the active region 468 of the third filter block. Theactive region 474 of the fourth filter block may enter a standby stateto prevent unnecessary power consumption.

The PRX RF Q unit 454 receives an RF signal of the LB, frequencydown-converts the received RF signal to a Q signal of the baseband, andforwards the baseband Q signal to the second filter block. The capacitorregion 464 of the second filter block is connected with the capacitorregion 462 of the first filter block, such that the capacitor region 462of the first filter block and the capacitor region 464 and the activeregion 466 of the second filter block operate for the Q signal of theLB. Variable capacitors included in the capacitor region 462 of thefirst filter block vary by a control signal of the active region 466 ofthe second filter block. The active region 460 of the first filter blockmay enter the standby state for power saving.

If the filter inputs are forwarded from the DRX RF I unit 456 and theDRX RF Q unit 458, channels are formed between the DRX RF I unit 456 andthe DRX RF Q unit 458 and some of the regions 462 through 472 of thefilter blocks by a switching unit 520, as shown in FIG. 5C.

More specifically, the DRX RF I unit 456 receives an RF signal of theLB, frequency down-converts the received RF signal to an I signal of thebaseband, and forwards the baseband I signal to the second filter blockthrough the switching unit 520. The capacitor region 464 of the secondfilter block is connected with the capacitor region 462 of the firstfilter block such that the capacitor region 462 of the first filterblock and the capacitor region 464 and the active region 466 of thesecond filter block operate for the I signal of the LB. The activeregion 460 of the first filter block may enter the standby state forpower saving.

The DRX RF Q unit 458 receives an RF signal of the LB, frequencydown-converts the received RF signal to a Q signal of the baseband, andforwards the baseband Q signal to the third filter block. The capacitorregion 470 of the third filter block is connected with the capacitorregion 472 of the fourth filter block, such that the active region 468and the capacitor region 470 of the third filter block and the capacitorregion 472 of the fourth filter block operate for the Q signal of theLB. The active region 474 of the fourth filter block may enter thestandby state for preventing unnecessary power consumption.

As such, in the 2G mode, capacitors allocated to a neighbor path areconnected in parallel to capacitors of a signal path for the 2G mode,thereby securing the expanded capacitor capacitance for signal processof the 2G mode.

A frequency range may be extended up to a 3-fold range by separatecontrol of a capacitor bank according to a mode, and by capacitorsharing according to an exemplary embodiment of the present invention, a6-fold frequency range may be supported. Moreover, each resistor of ananalog filter may be replaced with four resistance segments which areconnected in series or in parallel, thereby extending a resistor valueto a 16-fold resistor value range. In this way, a frequency range may beextended up to a 96-fold range.

FIG. 6 is a diagram illustrating a resistor block which varies accordingto a mode according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the illustrated resistor block may substitute forat least one of the input resistor R_(a) and the feedback resistor R_(b)of an analog filter, and are controlled according to gain, cut-offfrequency, and mode. As shown in FIG. 6, a resistor block 600 includesfour variable resistance segments 602, 604, 606, and 608, which areconnected in parallel between an input terminal R_(in) and an outputterminal R_(out). Input stages of the respective resistance segments 602through 608 are connected to the input terminal R_(in) through switchessw1 through sw4 and output stages thereof are connected to the outputterminal R_(out) through switches sw8, sw10, sw11, and sw13. A switchsw9 is connected between the output stage of the first resistancesegment 602 and the output stage of the second resistance segment 604. Aswitch sw6 is connected between the input stage of the second resistancesegment 604 and the output stage of the third resistance segment 606. Aswitch sw12 is connected between the output stage of the thirdresistance segment 606 and the output stage of the fourth resistancesegment 608. In addition, a switch sw5 is connected in parallel to theresistance segments 602 through 608, and a switch sw7 is connectedbetween the input stage of the fourth resistance segment 608 and theoutput stage of the switch sw5.

When each resistance segment has a resistance R_(x), the switches sw1through sw13 are controlled according to a gain, a cut-off frequency,and a mode, such that a total resistance of the resistor block 600 mayvary in a range of ¼ through 4 times of R_(X).

According to an exemplary embodiment according to FIG. 6, only theswitches sw1 and sw8 are turned on and the other switches are turnedoff. Thus, a total resistance of the resistor block 600 is R_(X) due tothe first resistance segment 602. By controlling on/off of the switchesin this way, a total resistance of the resistor block 600 may becontrolled to be in a range of ¼ through 4 times of R_(X).

FIGS. 7A through 7F are diagrams illustrating diverse connections of aresistor block according to an exemplary embodiment of the presentinvention.

Referring to FIG. 7A, in Mode 1, such as the 2G mode, for processing theLB, four resistance segments 702 of the resistor block are seriallyconnected by the switches sw1, sw9, sw6, sw12, and sw7, and the otherswitches are turned off, such that a total resistance is 4R_(X).

Referring to FIG. 7B, in Mode 2, third and fourth resistance segments704 are serially connected by the switches sw3, sw12, and sw7, and theother switches are turned off, such that a total resistance is 2R_(X).

Referring to FIG. 7C, in Mode 3, only a first resistance segment 706 isconnected between input and output terminals by the switches sw1 andsw8, and the other switches are turned off, such that a total resistanceis R_(X).

Referring to FIG. 7D, in Mode 4, third and fourth resistance segments708 are connected between input and output terminals by the switchessw3, sw11, sw4, and sw13, and the other switches are turned off, suchthat a total resistance is 0.5R_(X).

Referring to FIG. 7E, in Mode 5, four resistance segments 710 areconnected in parallel between the input and output terminals by theswitches sw1, sw2, sw3, sw4, sw8, sw10, sw11, and sw13, and the otherswitches are turned off, such that a total resistance is ¼R_(X).

Referring to FIG. 7F, in Mode 6, which is a bypass mode, all switchesexcept for the switch sw5 are turned off, such that the input and outputterminals are directly connected without passing through resistancesegments 712.

A unit resistance segment R_(X) is configured to vary according to again needed for each filter stage, and generally, a desired gain rangesfrom −12 dB to +24 dB, and a rate of input resistance segments andfeedback resistance segments is correspondingly adjusted.

FIG. 8 is a circuit diagram of an analog baseband filter apparatusaccording to an exemplary embodiment of the present invention.

Referring to FIG. 8, the analog baseband filter apparatus includes fourfilter blocks 808 a, 808 b, 808 c, and 808 d, and a DRX I signal, a DRXQ signal, a PRX Q signal, and a PRX I signal are respectively input toan input switching unit 806 through respective ones of a plurality offrequency converters 802 and a plurality of amplifiers 804. The inputswitching unit 806 forwards the input signals to at least two of thefilter blocks 808 a through 808 d according to a currently operatingcommunication mode under control of a controller (not shown). In the3G/4G modes, the input switching unit 806 forwards the four inputsignals to the four filter blocks 808 a through 808 d, respectively. Inthe 2G mode, the input switching unit 806 forwards 2G I and Q signals,which are input from DRX RF units through DRX I and Q input terminals,to the second and third filter blocks 808 b and 808 c, in which the 2G Qsignal from the DRX RF Q unit is forwarded to the second filter block808 b and the 2G I signal from the DRX RF I unit is forwarded to thethird filter block 808 c. In another exemplary embodiment of the presentinvention, in the 2G mode, the input switching unit 806 forwards 2G Iand Q signals, which are input from PRX RF units through PRX I and Qinput terminals, to the second and third filter blocks 808 b and 808 c,in which the 2G Q signal from the PRX RF Q unit is forwarded to thethird filter block 808 c and the 2G I signal from the PRX RF I unit isforwarded to the second filter block 808 c.

A description will be made of each filter block, representatively, thefirst filter block 808 a. The first filter block 808 a includes threefilter stages and an amplification stage 816. The three filter stagesinclude an RP filter 810, a first BQ filter 812, and a second BQ filter814. The respective filter stages of the first filter block 808 aindependently operate in the 3G/4G modes, and are not connected withfilter stages of the second filter block 808 b. In the 2G mode,capacitors C₁ of the RP filter 810 are disconnected with an OP AMP A andare connected in parallel to capacitors C_(1X) included in an RP filterof the second filter block 808 b, and the OP AMP A is turned off.Likewise, in the 2G mode, capacitors C₂, C₃, C₄, and C₅ of the nextfilter stages are disconnected with OP AMPs B, C, D, and E and areconnected in parallel to corresponding capacitors C_(2X), C_(3X),C_(4X,) and C_(5X) of the second filter block 808 b, and the OP AMPs B,C, D, and E are turned off.

Output signals of the filter blocks 808 a through 808 d are connected tocorresponding output stages through an output switching unit 818controlled by the controller. In the 3G/4G modes, the output switchingunit 818 connects output signals from the filter blocks 808 a through808 d to respective outputs including a DRX Iout, a DRX Qout, a PRXQout, and a PRX Iout. In the 2G mode, the output switching unit 818connects an output signal from the third filter block 808 c to a 2G Ioutoutput and an output signal from the second filter block 808 b to a 2GQout output.

FIGS. 9A and 9B are diagrams illustrating in detail connection ofcapacitors according to an exemplary embodiment of the presentinvention.

Referring to FIG. 9A, a first OP AMP 902 is positioned in the firstfilter block 808 a (see FIG. 8) and is connected in parallel to twocapacitors C₁₁ and C₂₁. A second OP AMP 904 is positioned in the secondfilter block 808 b (see FIG. 8) and is connected in parallel to twocapacitors C₁₂ and C₂₂. The capacitor C₁₁ is connected in parallel withthe first OP AMP 902 through the switches sw1 and sw2. The switch sw3 isconnected between input stages of the capacitors C₁₁ and C₁₂, and theswitch sw4 is connected between output stages thereof. Likewise, thecapacitor C₂₁ is connected in parallel with the second OP AMP 904through the switches sw5 and sw6. The switch sw7 is connected betweeninput stages of C₂₁ and C₂₂, and the switch sw8 is connected betweenoutput stages thereof.

In the 3G/4G modes, the switches sw1 and sw2, which connect thecapacitor C₁₁ to the first OP AMP 902, and the switches sw5 and sw6,which connect the capacitor C₂₁ to the second OP AMP 904, are turned on,or in other words, are closed, and the switches sw3 and sw4, whichconnect the capacitors C₁₁ and C₁₂ to each other, and the switches sw7and sw8, which connect the capacitors C₂₁ and C₂₂ to each other, areturned off, or in other words, are opened. Accordingly, capacitorsoperate in a corresponding filter block.

Referring to FIG. 9B, in the 2G mode, the switches sw3 and sw4, whichconnect the capacitors C₁₁ and C₁₂ to each other, and the switches sw7and sw8, which connect the capacitors C₂₁ and C₂₂ to each other, areturned on, and the switches sw1 and sw2, which connect the capacitor C₁₁of the first filter block 808 a to the first OP AMP 902, and theswitches sw5 and sw6, which connect the capacitor C₂₁ of the firstfilter block 808 a to the second OP AMP 904, are turned off.Accordingly, the capacitors C₁₁ and C₂₁ are connected in parallel to thesecond OP AMP 904 of the second filter block 808 b instead of the firstfilter block 808 a. In this case, the first OP AMP 902 of the firstfilter block 808 a may be turned off in order to save power. Otherfilter stages and capacitors of other filter blocks are connected andcontrolled in a similar manner according to an applied communicationmode, such that they may be shared between the 2G mode and the 3G/4Gmodes.

As is apparent from the foregoing description, in the 2G mode, acapacitor region for a diversity path of the 3G/4G modes is shared, andan architecture of input and feedback resistors is improved. Inaddition, a receiver system and a digital control code are provided inwhich input and output paths are variable according to a mode, such as a2G mode and a 3G/4G mode. Therefore, according to the exemplaryembodiments of the present invention, a variable-gain amplifier andfilter circuit and algorithm may be provided in which a gain and abandwidth needed for a baseband receiver are effectively implemented forall mobile communication standards supported in 2G, 3G, and 4G.

Moreover, when compared to the related art, the circuit area may bereduced by half or more, thereby reducing the cost and decreasing thenoise in the circuit. Furthermore, in next-generation mobilecommunication techniques, the present invention may be effectivelyapplied to configuration of a Multiple Input Multiple Output (MIMO)receiver structure such as a 4×2, a 4×4, an 8×4, or any other similarand/or suitable receiver structure.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. An analog baseband filter including a pluralityof Radio Frequency (RF) units configured to respectively receive RFsignals of a respective frequency band and output baseband signals for amulti-mode and multi-band wireless transceiver, the analog basebandfilter comprising: a plurality of filter blocks configured to filter andamplify the baseband signals output by the plurality of RF units, eachof the plurality of filter blocks having a capacitor region; and aswitching unit configured to connect at least one of the plurality offilter blocks to at least two of the plurality of RF units, wherein theat least one of the plurality of filter blocks is configured to beconnected to a capacitor region of an adjacent filter block.
 2. Theanalog baseband filter of claim 1, wherein the switching unit connectsthe at least two of the plurality of RF units to the at least one of theplurality of filter blocks according to a selected communication mode.3. The analog baseband filter apparatus of claim 1, wherein theplurality of RF units comprise at least one RF unit which is configuredto output In-phase (I) and Quadrature-phase (Q) signals corresponding toan RF signal of a first High Band (HB) of the plurality of frequencybands in a first communication mode and output I and Q signalscorresponding to an RF signal of a Low Band (LB) of the plurality offrequency bands in a second communication mode.
 4. The analog basebandfilter apparatus of claim 3, wherein the plurality of filter blockscomprise at least one filter block which is expanded to include acapacitor region of an adjacent filter block from among the plurality offilter blocks in the second communication mode, and receive I and Qsignals of the LB from the at least one RF unit and filter and amplifythe received I and Q signals.
 5. The analog baseband filter apparatus ofclaim 4, wherein, when in the second communication mode, capacitorregions of the at least one filter block share active elements of theadjacent filter block, and the active elements of the adjacent filterblock are turned off.
 6. The analog baseband filter apparatus of claim1, wherein capacitor regions of each of the filter blocks of theplurality of filter blocks are disposed adjacent to a capacitor regionof an adjacent filter block of the plurality of filter blocks.
 7. Theanalog baseband filter apparatus of claim 1, wherein each of theplurality of filter blocks comprises at least one of an input resistorand a feedback resistor, wherein, each of the at least one of the inputresistor and the feedback resistor comprise a plurality of variableresistance segments configured to be connected in parallel or in seriesthrough switches, and wherein the switches are turned on or offaccording to a communication mode and a predetermined gain.